1. Field of the Invention
The present invention relates to transfer devices and image forming devices.
2. Description of the Related Art
In an electrophotographic image forming device, in general, a direct-current voltage is applied from a transfer power supply to an electrostatic toner pattern created on an image carrier to move a developer such as toner constituting the electrostatic toner pattern to paper and transfer the electrostatic toner pattern to the paper.
When print is produced on paper with low surface smoothness having large asperities on the surface thereof such as Leathac paper or Japanese paper, a developer is less prone to be transferred to indentations than protrusions on the surface, which causes a problem that light print is made at the indentations.
Accordingly, there has been suggested a technique for improving the rate of transferring a developer to indentations by superimposing an alternating-current voltage on a direct-current voltage for transfer to vibrate the developer (for example, see Japanese Patent Application Laid-open No. 2012-42835).
However, the foregoing conventional technique is based on the premise that a power supply has an integration of a direct-current power supply and an alternating-current power supply. Thus, it cannot be said that the conventional technique provides an optimum power supply to achieve functionality needed by customers.
For example, no alternating-current power supply is required by customers who do not need printing on paper with low surface smoothness. In this case, the foregoing conventional technique provides an overengineered power supply.
As a measure, power supplies without an alternating-current power supply may be prepared (developed) for customers who do not need printing on paper with low surface smoothness. However, this measure leads to increase in man-hour for the development and management cost. In addition, even if users do not initially need printing on paper with low surface smoothness, they may afterward need printing on paper with low surface smoothness.
The present invention is devised in light of the foregoing circumstances. There is a need to provide a transfer device and an image forming device that offer an optimum power supply to achieve functionality needed by customers.